Call user defined sigwinch and sigcont handler

[tompng]

Fixes #735

Considering this kind of code. This code doesn't work well.

height, width = STDIN.winsize
Signal.trap(:WINCH){ height, width = STDIN.winsize }

loop do
  cui_game_render(width, height)
  if game_requires_user_text_input
    user_input = Reline.readline('>')
  end
end

User defined WINCH handler won't be called when window size is changed while reading input in Reline.readline. Same for SIGCONT.
This pull request fixes it.

We don't need to consider about user-defined WINCH handler prints something and corrupt Reline's screen. User-defined handler is expected to never print to STDOUT.

Signal.trap(:WINCH) do
  # This code has a possibility of `deadlock; recursive locking (ThreadError)`
  puts "winsize changed"
  clear_screen
  rerender_game_screen
end
loop{print "\e[H";sleep 0.0001}

[ima1zumi]

LGTM!